A rare cloud formation awed onlookers at the Queensland and New South Wales border on July 4. Roll clouds – also known as Morning Glory or arcus clouds – are a low, horizontal formation that can signal microburst activities such as sudden downdraught or powerful air currents. They are considered rare by meteorologists and weather enthusiasts. This video was taken at Goondiwindi, Queensland. Credit: Jennifer Smith via Storyful

July 7th 2017

2 years ago

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A rare iridescent cloud seen above Queensland, similar to the clouds spied in Darwin this week. Picture: Susie Cox.Source:Supplied

WE’VE heard of clouds having silver linings, but Northern Territory locals have been treated to the sight of clouds with a stunning rainbow lining.

On Sunday, just before a storm hit Darwin, several clouds began to shimmer with a multicoloured glow.

Those who saw it took to social media to try and describe the phenomenon. One called it an “ice prism,” another a “cloud bow” due to its resemblance to a rainbow.

“It’s incredible,” said an Instagram user. “I’m totally not doing this justice”.

A spectacular cloud formation caught the attention of Darwin residents during Sunday's storms.Source:Supplied

Peter Markworth, from the Bureau of Meteorology said the iridescent aura around the cloud was rarely seen and was due to a combination of perfect timing and conditions.

“The rare phenomenon occurs when sunlight diffracts through a high density of ice crystals which bend the light, creating a stunning colour.”

Mr Markworth said the light show over the Cox Peninsula was the same science as the iridescence of soap bubbles or opals.

“The cloud in which the colours formed is known as ‘pileus’ which forms from water vapour condensing and freezing into uniform ice crystals as a result of the very fast updraft from the storm.

“Very specific angles are needed to see the colours, so the position and height of the storm, the angle of the sun and the size of the ice crystals all came together to give Darwin a rare, perfect view of the iridescence.”

Like a giant rolling pin, it tumbles across the sky as fast as a car. Sometimes rows of the clouds line up giving the appearance of a freshly ploughed field in the sky.

Local Aboriginal people call it the kangólgi and the cloud’s arrival is a good omen that bird numbers will soon boom.

Gliders from all across Australia gather in Burketown, northern Queensland, each spring to grab the opportunity to ride the Morning Glory.

Bureau forecaster Andrew Bufalino, told news.com.au the Morning Glory, also known as a roll cloud, only forms in early to mid-spring when two sea breezes meet.

“They are usually about 1-2km in height and can span up to 1000km in length,” he said.

Two fronts meet over Cape York and head west across the Gulf of Carpentaria. At night, air over the Cape cools and slips under a layer of warm air to form “turbulent cylinder-like waves,” that roll across the waters and then dissipate over land, Mr Bufalino said.